These investigations are directed toward continuation of our detailed evaluation of electrolyte transport in the large intestine and its alteration in disease. These studies will evaluate: 1.) normal ion movement; 2.) the mechanism of electrolyte secretion produced by bile salts, hydroxy fatty acids, Shigella enterotoxin; and 3.) evaluation of agents that may interfere with electrolyte secretion. The methods that will be employed to study electrolyte transport in both man and experimental animal will include: a.) transmural ion transport under short-circuited conditions; b.) direct mucosal influx; and c.) in vivo continuous perfusion. The results of these investigations should provide meaningful information regarding electrolyte movement in both health and disease.